Advances in semiconductor integrated circuit (IC) design, processing, and packaging technologies have resulted in increases in the number and density of input/output (I/O) pads on each die. Nonetheless, the size of portable electronic systems such as portable computers, cell phones, PDAs, etc. continues to shrink despite the addition of new features and functions. New features and functionalities, such as digital cameras and camcorders, global positioning systems, and removable memory cards are continually being integrated into modern portable and/or high density electronic systems. It is desirable to decrease the thickness of the components within portable electronic systems to provide size reduction as well as additional space to add new components.
Although the length and width of portable electronic systems are constrained by the need to provide a comfortable user interface typically including an easy to use keypad and/or an easy to read display, there is a range in the acceptable physical sizes for each class of system at any point in time. However, over time, the size of most portable electronics systems tends to decrease.
As the manufactured sizes of systems and components continue to decrease, management of energy consumption and heat dissipation become increasingly important both at the level of the system and at the individual components level. Less space is available for power sources and heat dissipation structures. At the level of packaging and interconnect, this means that strategies and solutions are required to provide adequate thermal management and to accommodate the stresses generated by mismatches in thermal coefficient of expansion (TCE) occurring at the interfaces between components.
Reductions in size and thickness of components are also consistent with performance improvements due to reductions in signal path lengths between components. Despite increases in the number and density of input/output (I/O) pads on each die, the footprint and thickness of electronic systems continues to shrink since the individual components and/or devices integrated into these systems tend to decrease with each successive technology generation. Historically, electrical interconnections were formed as individual components, e.g. contacts, using conventional fabrication technologies such as metal stamping and bending. Using conventional assembly methods, individual contacts are assembled into a finished contactor and/or connector. Conventional fabrication and assembly methods become increasingly complex and expensive as the number and density of the contacts increases.
Micro-fabricated spring contacts are capable of overcoming many of the limitations associated with conventionally fabricated spring contacts. Micro-fabricated spring contacts can be fabricated using a variety of photolithography based techniques known to those skilled in the art, e.g. Micro-Electro-Mechanical Systems (MEMS) fabrication processes and hybrid processes such as using wire bonds to create spring contact skeletons and MEMs or electroplating processes to form the complete spring contact structure. Arrays of spring contacts can be either be mounted on a contactor substrate by pre-fabricating and transferring them (either sequentially or in mass parallel) to the contactor substrate or by assembling each element of the spring contact array directly on the contactor substrate using a wire bonder along with subsequent batch mode processes, e.g. electroplating, as disclosed in U.S. Pat. No. 6,920,689 (Khandros et al.), U.S. Pat. No. 6,827,584 (Mathieu et al.), U.S. Pat. No. 6,624,648 (Eldridge et al.); U.S. Pat. No. 6,336,269 (Eldridge et al.), U.S. Pat. No. 5,974,662 (Eldridge et al.), U.S. Pat. No. 5,917,707 (Khandros et al.), U.S. Pat. No. 5,772,452 (Dozier et al.), and U.S. Pat. No. 5,476,211 (Khandros et al.).
Alternatively, an array of micro-fabricated spring contacts can be fabricated directly on a contactor substrate utilizing thick or thin film photolithographic batch mode processing techniques such as those commonly used to fabricate semiconductor integrated circuits. Numerous embodiments of monolithically micro-fabricated photolithographic spring contacts have been disclosed such as those by Smith et al in U.S. Pat. No. 6,184,699, Mok et al. in U.S. Pat. Nos. 6,791,171 and 6,917,525, and Lahari et al in US Patent Pub. No. US-2003-0214045-A1.
Semiconductor wafer probe card assembly systems are used in integrated circuit (IC) manufacturing and testing to provide an array of spring contact probes for making contact to the electrical interconnection pads on each of the semiconductor devices on the wafer. An additional function of probe card assembly systems is to translate electrical signal paths from the tightly spaced electrical interconnection pads on ICs to the coarsely spaced electrical interconnection pads on printed circuit boards that interface to IC test systems.
Semiconductor wafer probe cards are typically required to accommodate increases in the density and number of input/output (I/O) pads on each die, as well as increases in the diameter of the silicon wafers used in IC fabrication processes. With more die to test per wafer and each die having more I/O pads at higher densities, the cost of testing each die becomes a greater and greater fraction of the total device cost. This trend can be minimized or even reversed by reducing the test time required for each die or by testing multiple die simultaneously. If multiple die are tested simultaneously, then the requirements for parallelism between the probe tips and the semiconductor wafer and the co-planarity of the probe tips become increasingly stringent since all of the probe tips are required to make good electronic contact at the same time over a large area on the wafer or the entire wafer in the case of wafer level test and/or burn-in.
To test more than one die on a semiconductor wafer simultaneously, simultaneous low-resistance electrical contacts must be established with positionally matching sets of spring contact probes for each die to be tested and maintained over a broad temperature range. The more die to be tested simultaneously, the greater the degree of parallelism that is required between the spring probes and the surface of the semiconductor wafer, to insure that the probe tip “scrub”, and hence electrical contact, is uniform across the wafer. However, as higher numbers of die are tested in parallel, the number of simultaneous interconnects from the IC to the probe card assembly to the IC tester increases (not assuming pin multiplexing). Since probe tips for contacting the bonding pads on IC wafers require sufficient mechanical force on a per connection basis to assure a reliable low resistance connection, the total force between the probe card assembly and the wafer increases in proportion to the number of connections.
Similar trends are seen in connector, device packaging, and socketing applications, although specific requirements may vary for each specific application. For example, probe scrub damage requirements for probe cards which contact the bonding pads, e.g. such as comprising aluminum, gold, copper, solder, etc., on bare die are different those for sockets which contact the leads, terminals, bumps, etc., e.g. such as comprising gold, copper, solder, etc., or solder balls, of packaged die or those for packaged devices or connectors in which contact is made to contact pads, e.g. such as comprising gold, copper, solder, etc. on a printed circuit board. Nonetheless, increases in die size and/or the density and number of input/output (I/O) pads on each die, and/or use case temperature extremes tend to drive up the complexity and cost of the electrical interconnect structures required in all of the above applications. Compensation for lack of co-planarity is also an important requirement for connectors, packages and sockets, particularly as connection areas and die size increases and/or as component thicknesses decrease.
In some types of IC devices such as memory and microprocessors, die sizes continue to increase whereas for other types of devices such as mixed signal and analog, die sizes have decreased as a result of numerous technological advances. Nonetheless, in many cases, decreases in bond pad sizes, and/or increases in the density and/or number of (I/O) pads is driving the need for cost effective and high performance miniaturized interconnects for connector, device packaging, and socketing applications.
Additionally, there is a need for improved methods for providing temporary electrical connections in which a connection is made for a short time, for example, in probe card or system testing applications. There is also a need for improvements in demountable electrical connections in which it is desirable to maintain a reliable connection for extended time periods but it may be desired to non-destructively beak the connections, for example, in system in package or memory module applications where it is desirable to be able to demount and remount a device or modular package within a larger system for the purposes including but not limited to product development, field or depot upgrade, configuration change, or repair. Additionally, there is a need for improved methods of providing reliable and low cost permanent electrical connections.
It would be advantageous to provide micro-fabricated spring contacts at a relatively low cost per contact that maintain low resistance electrical connections for a variety of contact geometries and metallurgies, at high connection densities, over large or small areas, over a wide temperature range, and/or at high frequencies. Such micro-fabricated spring contacts would constitute a major technical advance.
It would be advantageous to provide micro-fabricated spring contacts at a relatively low cost per contact that maintain low resistance electrical connections for a variety of contact geometries and metallurgies with relatively low contact forces, at high connection densities, over large areas, over a wide temperature range, and/or at high frequencies. Such micro-fabricated spring contacts would constitute a major technical advance.
It would be advantageous to provide contactors incorporating micro-fabricated spring contacts at a relatively low cost per contact that maintain low resistance electrical connections, at high connection densities, over large areas, over a wide temperature range, and/or at high frequencies. Such a contactor would constitute a major technical advance.
It would be advantageous to provide contactors incorporating micro-fabricated spring contacts at a relatively low cost per contact that accommodate mismatches in the thermal coefficient of expansion (TCE) between integrated circuit devices and the next level of interconnect while providing and efficient means for meeting all thermal management requirements. Such contactors would constitute a further major technical advance.
It would be further advantageous to provide contactors incorporating micro-fabricated spring contacts having sufficient mechanical compliance to perform functions including but not limited to accommodating the planarity requirements of one or more electronic devices with the same or multiple or varying thicknesses, multiple devices across a wafer, one or more devices or device types in a single package or module, meeting planarity compliance requirements for high-density sockets and connectors, as well providing simultaneous electrical connections and Z-compliance with spring forces appropriate to meet the requirements of electronic systems including but not limited to adjustable optical interfaces such as auto focus mechanisms for cameras and projectors and other applications in electronic systems including but not limited to computers, portable computers, personal digital assistants (PDAs), medical devices, cameras, printers, imaging devices, cell phones, and the like. Such contactors would constitute a further major technical advance.
Furthermore, it would be advantageous to provide means for latching between assembly structures incorporating micro-fabricated spring contacts in temporary, demountable, and permanent applications. Such assembly structure latching means would constitute a further technical advance.